import sys

import pygame

from alien import Alien
from bullet import Bullet
from settings import Settings


def check_events(ai_settings, screen, ship, bullets):
    # 响应按键和鼠标事件
    for event in pygame.event.get():
        if event.type == pygame.QUIT:
            sys.exit()
        elif event.type == pygame.KEYDOWN:
            check_key_down_events(event, ai_settings, screen, ship, bullets)
        elif event.type == pygame.KEYUP:
            check_key_up_events(event, ai_settings, screen, ship, bullets)


def check_key_down_events(event, ai_settings, screen, ship, bullets):
    if event.key == pygame.K_RIGHT:
        # 向右移动飞船
        # ship.rect.centerx += 1
        ship.moving_right = True
    elif event.key == pygame.K_LEFT:
        # 向左移动飞船
        # ship.rect.centerx -= 1
        ship.moving_left = True
    if event.key == pygame.K_UP:
        # 向右移动飞船
        # ship.rect.centerx += 1
        ship.moving_top = True
    elif event.key == pygame.K_DOWN:
        # 向左移动飞船
        # ship.rect.centerx -= 1
        ship.moving_bottom = True
    elif event.key == pygame.K_SPACE:
        fire_bullet(ai_settings, bullets, screen, ship)
    elif event.key == pygame.K_q:
        sys.exit()


def fire_bullet(ai_settings, bullets, screen, ship):
    """如果还没有到达限制，就发射一颗子弹"""
    if len(bullets) < ai_settings.bullets_allowed:
        new_bullet = Bullet(ai_settings, screen, ship)
        bullets.add(new_bullet)


def check_key_up_events(event, ai_settings, screen, ship, bullets):
    if event.key == pygame.K_RIGHT:
        ship.moving_right = False
    elif event.key == pygame.K_LEFT:
        ship.moving_left = False
    elif event.key == pygame.K_UP:
        ship.moving_top = False
    elif event.key == pygame.K_DOWN:
        ship.moving_bottom = False


def update_screen(ai_setting, screen, ship, bullets, aliens):
    # 更新屏幕上的图像，并切换到新屏幕
    # 每次循环时都重绘屏幕
    screen.fill(ai_setting.bg_color)
    for bullet in bullets:
        bullet.draw_bullet()
    ship.blitme()
    aliens.draw(screen)
    pygame.display.flip()


def update_bullets(ai_settings,bullets, aliens):
    """更新子弹位置，并删除已消失的子弹"""
    # 更新子弹的位置
    bullets.update()
    # 删除已经消失的子弹
    for bullet in bullets:
        if bullet.rect.bottom <= 0:
            bullets.remove(bullet)
    # print("屏幕上剩余子弹数量：" + str(len(bullets)))
    # 检查是否有子弹击中了外星人 ，如果是这样，就删除相应的子弹和外星人
    collisions = pygame.sprite.groupcollide(bullets, aliens, True, True)
    if len(aliens) == 0:
        # 删除现有的子弹并且新建一群外星人
        bullets.empty()
        create_fleet(ai_settings, screen, ship, aliens)


def create_fleet(ai_settings, screen, ship, aliens):
    """创建外星人群"""
    # 创建外星人，并计算一行可容纳多少个外星人
    # 外星人间距为外星人的宽度
    alien = Alien(ai_settings, screen)
    alien_width, number_aliens_x = get_number_aliens_x(ai_settings, alien)
    number_rows = get_number_rows(ai_settings, ship.rect.height, alien.rect.height)
    # 创建第一行外星人
    for row_number in range(number_rows):
        for alien_number in range(number_aliens_x):
            create_alien(ai_settings, screen, aliens, alien_number, alien_width, row_number)


def create_alien(ai_settings, screen, aliens, alien_number, alien_width, row_number):
    """创建一个外星人"""
    # 创建一个外星人并将其加入当前行
    alien = Alien(ai_settings, screen)
    alien.x = alien_width + 2 * alien_width * alien_number
    alien.rect.x = alien.x
    alien.rect.y = alien.rect.height + 2 * alien.rect.height * row_number
    aliens.add(alien)


def get_number_aliens_x(ai_settings, alien):
    """计算每行可以容纳多少个外星人"""
    alien_width = alien.rect.width
    available_space_x = ai_settings.screen_width - 2 * alien_width
    number_aliens_x = int(available_space_x / (2 * alien_width))
    return alien_width, number_aliens_x


def get_number_rows(ai_settings, ship_height, alien_height):
    """计算屏幕可以容纳多少行外星人"""
    available_space_y = (ai_settings.screen_height - (3 * alien_height) - ship_height)
    number_rows = int(available_space_y / (2 * alien_height))
    return number_rows


def update_aliens(ai_settings: Settings, aliens):
    """更新外星人群中所有外星人的位置"""
    check_fleet_edges(ai_settings, aliens)
    aliens.update()


def change_fleet_direction(ai_setting: Settings, aliens):
    """将整群外星人下移，并改变它们的方向"""
    for alien in aliens:
        alien.rect.y += ai_setting.fleet_drop_speed
    ai_setting.fleet_direction *= -1


def check_fleet_edges(ai_setting: Settings, aliens):
    """有外星人到达边缘时采取相应的措施"""
    for alien in aliens:
        if alien.check_edges():
            change_fleet_direction(ai_setting, aliens)
            break
